Answer: b
Explanation: PCR uses the enzyme DNA polymerase that directs the synthesis of DNA from deoxynucleotide substrates on one stranded DNA template. DNA polymerase synthesizes DNA in a 5’→3’ direction and can add nucleotides in the 3’ end of a custom – designed oligonucleotide.

Answer: a
Explanation: A synthetic oligonucleotide is annealed to a single stranded DNA template that contains a complementary region. DNA polymerase thus uses this annealed primer to elongate the new strand.

Answer: a
Explanation: Two single stranded, oligonucleotide is synthesized and used as a primer. The primers thus produces binds to the denatured DNA and polymerase starts its synthesis in the 5’ to 3’ direction.

Answer: c
Explanation: Amplification is usually carried out by the DNA polymerase I enzyme from Thermus aquaticus. As this organism lives in hot springs, Taq polymerases are thermostable thus they are resistant to high temperature.

Answer: c
Explanation: After each cycle the number of duplexes doubles itself thus after the first cycle there are 2 DNA duplexes. A duplex has 2 DNA strands thus after second cycle there will be 4 Duplexes, after third cycle there will be 8 DNA duplex. Lastly, after the 4th cycle there will be 16 duplexes.

Answer: d
Explanation: The polymerase chain reaction is started by heating the mixture at 94˚C. At this temperature the hydrogen bonding between the nucleotide bases melts thus separating the two DNA strands.

Answer: d
Explanation: After the denaturation of the two strands the temperature is decreased to 50 – 60˚C. At this temperature the primers anneal to their complementary segments. Thus as 54˚ lies within this range option b is the correct option.

Answer: a
Explanation: The DNA synthesis in polymerase chain reaction takes place at 74˚C. This is usually set at 74˚C because this is just below the optimum temperature of functioning of the Taq polymerase.